Afghanistan's already strict body searches may get even more intrusive after the intelligence service revealed that a suicide bomber who badly wounded the country's spy chief had concealed his explosives by wrapping them around his genitals.

The bomber had secured the face-to-face meeting in Kabul with Asadullah Khalid, head of the National Directorate of Security (NDS) since September, by posing as a Taliban messenger potentially interested in helping broker peace talks.

The blast left Khalid with injuries to his abdomen and lower body, but he has been stabilised and is expected to recover. The unusual placement of the bomb may have saved Khalid's life, as most of the force of the explosion appears to have been directed downwards.

"Thank God, he's OK. It's positive," the president, Hamid Karzai, said after visiting Khalid at an NDS hospital where he was recovering from surgery on Thursday evening. But the damaging attack on one of the most heavily protected men in the country underlined the resources and reach of the insurgency at a time when western forces are already heading home.

It brought back memories of the September 2011 assassination of the former president Burhanuddin Rabbani, when he was head of a government council seeking a negotiated end to the war. He was killed by a man also posing as an insurgent envoy who had hidden explosives inside his turban.

Thursday's attacker met Khalid at a city centre guesthouse used for meetings when he wanted more privacy than is possible at the spy agency's main headquarters. Security controls are less stringent, and although the attacker was searched at least once, his choice of hiding place for the bomb meant he escaped detection.

"The results of the NDS investigation regarding Thursday's terrorist attack shows that the designers of this suicide attack placed explosives around the genitals of the suicide bomber," the intelligence service said in an email.

This "is against all Islamic and cultural standards … and shows that the enemies of peace and stability in Afghanistan have no regard for Islamic teachings and standards".

The Taliban claimed responsibility for the blast, the fifth attempt on Khalid's life in as many years. Before taking up his current job he served as minister of tribal and border affairs, and had previously been governor of the unsettled eastern province of Ghazni, and the southern province of Kandahar, birthplace of the Taliban.